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Civilization 546 has discovered an old space engine after the ship crash-landed on their planet and killed the crew. Their aircraft are rather primitive, mainly WWI biplanes. Now that they have discovered this engine capable of speeds up to 700mph, does civilization 546 need to change their plane designs to cope with these speeds?

Assume that

  • the new engine takes place of the old one and is the same size/weight/shape
  • you can use datasheets for Sopwith Camel if you want to get that detailed
  • fuel is not needed, it is a nuclear reactor powered off of whatever molecules are available. It would eat the plane before it ran out of gas.

More details can be added upon request.

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    $\begingroup$ Engines are not "capable of speeds". Engines provide thrust. (Or in the case of the engines of propeller-driven aircraft, engines provide torque.) How the airframe translates thrust into speed has nothing to do with the engine. (And anyway, a spacecraft engine on an airplane frame makes no sense.) (And the speed limits of propeller aircraft have much more to do with the behaviour of air than with the power of the engine. In particular, a propeller-driven aircraft won't be able to fly faster than sound.) $\endgroup$
    – AlexP
    Oct 7, 2020 at 14:21
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    $\begingroup$ @AlexP -- True, however, an engine ìs capable of making something go a particular speed. Even if that something is a ripped to shreds Sopwith Camel. "Capable of speed X" is shorthand for "capable of sufficient thrust output that the object it is attached to can be made to travel at X speed". $\endgroup$
    – elemtilas
    Oct 7, 2020 at 14:50
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    $\begingroup$ @elemtilas Biplanes simply would not survive the stresses such an engine would impose. Even all-metal biplanes would only be designed to handle stresses close to the intended engine design - you don't design the airframe without some ideas of the areodynamic stresses the engine will impose on it in flight. Control surfaces designed for 150 mph probably won't survive 50% more speed, let alone near the speed of sound. $\endgroup$
    – StephenG - Help Ukraine
    Oct 7, 2020 at 15:30
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    $\begingroup$ At the end of the WWI the top speed of planes could be around 150 mph. Let's say you translate that to engine capability and replace the engine in a way that, on paper, the plane should go 700mph. But the properell get destroyed by the amount of turn it would be forced to do. $\endgroup$
    – SZCZERZO KŁY
    Oct 7, 2020 at 15:46
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    $\begingroup$ @AlexP Speed is plenty good a proxy for power, but what should be apparent is that the OP wants WWI planes that can go 700 mph. $\endgroup$
    – user458
    Nov 5, 2022 at 1:50

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It wouldn't work.

The fact is, WWI-era biplanes were not designed with high speeds in mind. As a result, even if the engine can provide enough thrust to get it to 700 miles per hour, the plane won't actually go 700 miles per hour—it'll go "boom". Rather spectacularly, at that. Late WWII is the earliest time that you could just strap that engine to a plane and have it (barely) work.

That being said, here's what you would have to do to make it work.

  1. Specially design the plane, using metal for the exterior surfaces and superstructure. The fabric and wood primarily used in that era simply can't hold up at such high speeds.

  2. Add an oxygen supply system for the pilot. WWI aircraft flew close to the ground, so they didn't need to supply air for the pilot. You can't realistically expect pilots of that era to be able to manage flying low at such great speeds; even today that requires years of training. As a result, the pilot will need to be supplied with air.

  3. Add some sort of G-force compensating gear. Unless, of course, you only want to fly in one direction.

That is, of course really oversimplified. Not that it matters - none of those things could realistically be done with WWI tech.

Also, it's worth mentioning that even if you do manage to accomplish all those things, the plane will be useless. It will simply be too fast to be effective.

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  • $\begingroup$ You don't need the oxygen supply: under current regulations, it's not required until you're flying above flight level 125 (12,500 feet, 3800 meters), and that's plenty high enough for flying too fast. $\endgroup$
    – Mark
    Nov 5, 2022 at 3:25
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Civilization 546 knows conventional and pusher propeller planes. That means there is an engine which rotates a shaft and a propeller mounted on that shaft, either pulling or pushing. Mounting a jet engine in place of a propeller engine would either roast the pilot or suck the pilot into the intake. Two options:

  • The spacecraft contained a magic technobabble reactionless engine which just happens to have roughly the right shape to be mounted in place of the old engine.
  • Civilization 546 rebuilds their airframe to mount the newfound engine. For instance, the Soviets experimented with auxiliary ramjets in the I-153DM biplane.

Assume that the newfound engine produces enough power to push a similar-sized spacecraft to 700 mph. The spacecraft probably has better streamlining, so the airplane won't get quite as fast as the spacecraft used to be. Or the spacecraft was supersonic and the 700 mph are what a wire-and-canvas contraption will do with that much power.

Issues include the open cockpit of period planes, the lack of oxygen systems, and a general inability to take the stresses from the engine. Without a complete rebuild, the old airframe will disintegrate as the test pilots try how fast it goes.

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You wouldn't recognize the "Sopwith Camel" anymore after all the changes necessary for 700mph.

The fastest WW2 era prop planes (I assume you want to keep the prop) could do 700mph in an emergency dive (wiki). They are far advanced from a WW1 era plane (mostly wood and fabric). It would definitely get ripped apart. Even those WW2 planes are late war and reach such speeds in emergency situations.

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  • $\begingroup$ 287 Squadron with their SE5's can forget about beating 266 if these Camels are around. $\endgroup$
    – user86462
    Nov 6, 2022 at 4:45
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Breaking the speed of sound with a prop plane is really hard, maybe impossible.

Back before Chuck Yeager reach Mach 1, there was research into trying to reach Mach 1 using prop planes. For reference, typical speed of sound at 35000 feet is around 640 mph, so 700 mph will be a problem with any prop plane.

You run into real problems in limits of thrust as your propellers approach the necessary speeds (which of necessity must be even faster than the planes forward airspeed). Thrust becomes less efficient as you approach sonic blade speed, but even worse, the propeller runs faster at the outer edge (supersonic) while the inner portion is subsonic - this causes terrible turbulence related problem that will likely destroy an advanced propeller plane with the flutter driven vibration, as well as increase the drag by a large amount - limiting forward airspeed.

Since jets can do the job with the ability yo far exceed Mach 1, there was little reason to continue this line of research.

Is there any possible work-around? Speed of sound depends upon the molecular weight of the gas - which is essentially fixed at around 29 for air. It also depends upon the temperature of the gas. The easiest solution to higher speeds is to heat the air your are flying through. You can find speed of sound calculators online (the formula is actually simple), I put in 500 F and get a speed of 1035 mph. At that temperature, 700 mph flight would be much easier to achieve with a propeller - there are actual prop planes in use that can reach Mach 0.7 in level flight.

So, you need to fly in some seriously heated air, and it certainly will require an advanced air frame - I would recommend some form of cooling the inside of the plane too. High altitude flight is also strongly recommended to reduce drag, etc.

Perhaps you can fly recon missions over active weapons tests - you'll need radiation protection gear too.

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